S&W MP 40 Mag. extensions

Hello,I have a MP 40 and would like to find mag extensions for it . I have posted this before and was directed to Taylor Freelance sold by Brownells.
However they only work with there magazines. Dose anyone have them that will work with stock S&W mags ?
I buy them from others to fit all my Glocks with no problems .
Any help would be thankfull.
GHR1142